With the surge in the crime rate, in general, and particularly in the burglary rate, there has been a proliferation of protective devices, directed mostly toward prevention of illegal entry through doors. Bars and gratings of various types have been placed across windows but, in addition to being unsightly, these constitute a serious danger in that they may prevent rapid escape in the event of fire. Moreover, such bars and gratings are limited in application since they are essentially permanent fixtures; such bars and gratings, therefore, cannot be used for giving an alarm if an intruder attempts entry through a door or a window in a hotel room or a state room on a ship.
Somewhat the same problem arises with respect to sliding doors of the type where a single door slides into a wall or the double type where either of a pair of sliding doors can be moved past the other. Also, it would be desirable if such a device could be used in connection with both double hung windows and windows that open on a hinge.
While complete prevention of illegal entry by intruders provides the ultimate in protection, nevertheless, an effective alarm system which is portable, sufficiently inexpensive and easily applied can provide a measure of protection whether one is at home or travelling. As is evident, an inexpensive but effective device which is reliable, readily installed and easily portable is greatly to be desired.